AVO in North of Paria, Venezuela: Gas methane versus condensate reservoirs

Abstract

The gas fields of North of Paria, offshore eastern Venezuela, present a unique opportunity for amplitude variations with offset (AVO) characterization of reservoirs containing different fluids: gas‐condensate, gas (methane) and water (brine). AVO studies for two of the wells in the area, one with gas‐condensate and the other with gas (methane) saturated reservoirs, show interesting results. Water sands and a fluid contact (condensate‐water) are present in one of these wells, thus providing a control point on brine‐saturated properties. The reservoirs in the second well consist of sands highly saturated with mathane. Clear differences in AVO response exist between hydrocarbon‐saturated reservoirs and those containing brine. However, it is also interesting that “subtle” but noticeable differences can be interpreted between condensate‐and methane‐saturated sands. These differences are attributed to differences in both in‐situ fluid density and compressibility, and rock frame properties.

Recent advances in seismic lithologic analysis

“…The ability to identify partial gas saturations is of obvious importance. In practice, careful petrophysical control and detailed modeling and/or inversion can potentially be used to identify fluid type (e.g., Regueiro and Pena, 1996;Cardamone and Corrao;. It is hoped that combined P-P and P-SV converted-wave AVO analysis will improve pore fluid identification.…”